Many pharmaceutical preparations are unstable when admixed in their carriers thus exhibiting substantially reduced potency and shelf-life, and the state of nature of many polymers and amalgamates necessitates separation into their component parts, until immediately prior to use.
In the case of plural component medications, such as vaccinations, liquid diluents and solid lyophilized components are maintained in separate glass vials with pierceable rubber stoppers. Preparation necessitates a lengthy mixing procedure wherein the stopper of the diluent vial is first pierced with a sterile needle and syringe, and the diluent withdrawn into the syringe. The needle is subsequently withdrawn from the first and inserted in to the second vial and the diluent injected thereto. The medication is admixed and withdrawn into the syringe for injection. In the case of most vaccinations which are typically given by the intramuscular or subcutaneous route, injection procedure requires that the plunger of the syringe be withdrawn slightly after insertion of the needle into the patient. If at that time the hypodermic has been placed into a blood vessel, blood will be aspirated into the syringe. This withdrawal test allows replacement of the needle to a nonintravascular site. This test is likewise performed to confirm intravascularity when a mixture is to be given intravascularly.
The inherent problems of said procedure include considerable expense in the form of: a lengthy procedure, high cost of separate containerization, storage and refrigeration, and the generation of a substantial quantity of medical waste, its problematic disposition and the consumption of resources, in a time where conservation is of particular importance.
Furthermore, repeated insertion and retraction of the sterile needle into the vial stoppers, which are externally unclean and contaminated with microbial organisms increases greatly the risk of contamination of a sterile medical preparation with external environmental contaminants.
Additionally, foreign body contamination by small rubber particles cut from the vial stoppers by the razor sharp bevelled needle, upon insertion, represents a hazard, as these may be injected along with the medication into the patient.
Those skilled in the prior art will recognize this similar disadvantage as seen with prior art apparatuses using pierceable or bursting diaphragms.
Solowey, in Canadian Pat. No. 891,356, teaches the use of a bursting diaphragm wherein a cap-like stopper plug with a bursting bottom is ruptured by pressure generated by a specially designed plunger which inserts into said cap in a male/female interaction, said cap then depressed with the plunger to expel the syringe contents.
The possibility for the ruptured membrane to dislodge and clog up the distal syringe aperture or enter the patient parenterally, is recognized. Said special plunger further necessitates complex specific manufacturing and limits expulsion due to its flat bottom.
Similar disadvantages are recognized with bulb type expulsion systems. Williams, in Canadian Pat. No. 766,545, teaches the use of a bulb type syringe which requires a screwing action and bursting of a diaphragm. Notwithstanding the complex thread machining, the shortcomings of inaccurate dosage are recognized.
Similarly, the prior art utilizing inserts may minimize the accuracy of dosage quantity delivered.
Of the various types of plural compartment containers taught in the patents, bypass type syringes require the movement of a partition into a bypass area, wherein a liquid phase is forced around said partition by the action of a plunger, so as to effect admixing.
There exists however, with regards to the herein above mentioned, a tendency toward a variety of disadvantages which include, a tendency for entrapment of medication at the bypass zone with retention of large residual volumes of medication in the syringe; a reverse propulsion of contents and more difficultly performed withdrawal test.
For instance, Canadian Pat. No. 894,352 (Walecka) utilizes a stopper and plunger that encases two compartments which communicate via an enlargement in the syringe body (bypass). As the plunger is depressed, the translation force moves said stopper into the enlargement or bypass zone. Disadvantageously, as the stopper passes the bypass zone enlargement site entering an area of normal diameter, it thereby seals off the distal compartment and precludes the inclusion of the entire volume of proximal medication in dispensation. Additionally, a fixed bypass fixes the volume of proximal and distal compartment sizes necessitating a specific syringe for each specific medication volume.
Szwarc, in Canadian Pat. No. 1,262,327, teaches a bypass arrangement wherein a slight enlargement placed laterally on the syringe body, sealed proximally by a movable stopper. As in the herein above mentioned bypass arrangement, fluid flows preferentially around the bypass until said stopper engages the distal non-bypass zone. At or about that point is encountered a tendency for retropulsion of a portion of the medical volume in a proximal or backward direction out of the syringe barrel, potentially aerosolizing harmful biologics or vaporous chemicals. To prevent said extra-syringation of medication, complex flanges must be included to catch the spilling medication.
It is known from the prior art that utilizing a cannular bypass like in Canadian Pat. No. 1,185,858 (Lissenburg et al), may create a tendency for difficult visualization of blood during the withdrawal test.
Zackheim, in Canadian Patent No. 888,333, teaches a valve seated across a syringe body propped up by a ledge. Upon depression of a plunger, said valve is moved off its ledge by tilting into a perpendicular orientation with respect to its original position, so as to effect fluid bypass and admixing of components. A tendency for said valve to remain perpendicular, thereby precluding expulsion of a fluid column approximately equal to the perpendicular height of said valve as it becomes entrapped at the distal inner syringe barrel in a perpendicular fashion by the plunger, is recognized.
Furthermore, smooth ejection is precluded, in that the ledge must be bypassed by the syringe plunger. This may lead to patient discomfort and pain due to the cutting action of the razor sharp, bevelled, moving needle in the patient's dermis or muscle, and hazard in the case of Veterinary Medicine, wherein rapid painfree injection is necessary in intractable animals.
Other prior valve sealing apparatuses include multi-component syringes (Canadian Patent No. 1,001,032) which require costly manufacturing and precision design.
Dupont et al, in U.S. Pat. No. 4,563,174, teach a syringe separated into parts by a complex rotatable seal valve double plunger system. The necessary precision and material usage makes this arrangement unsuitable for single use, being cost prohibitive and generating undue medical waste.
The syringe apparatuses herein above eluded to, represent plural-compartment containers but none have adequately addressed the need for a simple, cost effective, low wastage, reliable pluro-compartment mixing dispensing container. Doctors, and especially veterinary doctors, strongly recognize the need for a pluro-compartment mixing dispensing container which addresses the hereto mentioned medical requirements, while adaptable to current manufacturing procedures and current theories of conservation.